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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,243 records · Page 69
All sourcesNASA NTRSDOE OSTI
NASA NTRS1996

Feasibility Study of Velocity and Temperature Measurements of an Arcjet Flow using Laser Resonance Doppler Velocimetric (LRDV) Technique

Thermal Protection System (TPS) materials are used in space vehicles to shield from high heating environment encountered during their atmospheric reentry. Arcjet wind tunnels are used to simulate the flowfield encountered by the spacecrafts, and are used for testing TPS materials. How well these tests simulate the actual heating environment encountered by space vehicles depends on the characteristics of the simulated flow. The flow characterization requires the determination of temperature, concentration, and velocity of the various atomic and molecular species present in the flow. However, determining these parameters requires a complex set of both analytical and experimental procedures. The ability to properly simulate the flight environment is directly related to the accuracy with which these techniques can be used to define the arcjet Laser Resonance Doppler Velocimetric (LRDV) technique can be used to accurately determine the velocity and temperature of a gaseous species. In this technique, the medium is probed with a laser beam that is in resonance with an absorbing transition of the species. The absorption lineshape is Doppler-shifted due to the flow velocity of the species, and the frequency shift is detected as the variation in intensity of the fluorescence emitted by the species. Thus a measurement of the Doppler shift and the width of a spectral line can give both the temperature and the velocity of the flowfield. This summer, our project was to make a feasibility study to set up an experimental arrangement for the laser resonance Doppler velocimetric technique using a ring dye laser. Experiments required troubleshooting, cleaning, testing, and alignment of two lasers and several diagnostics instruments. All instruments and lasers necessary for the project worked well, but the output power of the broadband fundamental dye laser was limited to about 20 mW. This was quite low as compared to that necessary to obtain second harmonic oscillation at 327.49 nm for the LRDV studies. Further optimization of the dye laser optical elements is necessary before it can be used for the experiment, which requires narrowband (about 20 Mhz) laser operation.

Rob, Mohammad A.↗
DOE OSTI2025

Laser ablation of high-loading Li-ion battery electrodes improves accessible capacity and cycle life for Behind-the-Meter Storage

Adoption of Behind-the-Meter Storage (BTMS) requires design of batteries that enable high safety, long cycle life, and low cost at the system level. Pairing Li 4 Ti 5 O 12 (LTO) with LiMn 2 O 4 (LMO) achieves targets related to safety and cycle life, but these materials' low energy densities contribute to higher cost at the system scale. Increasing electrode loading is a simple approach to improve energy density, but comes with a trade-off in electrode utilization due to long, tortuous Li + diffusion pathways. Here, laser ablation is used to microstructure (pattern) high-loading electrodes to enhance electrode performance through improved Li + diffusion pathways. Four cell types, comprising combinations of standard or patterned anode and cathode, were prepared to evaluate the effects of laser ablation at each electrode. A rate test shows that patterning electrodes enhances active material utilization at ≳1C rates. Patterning the cathode yields the most benefit, as cells with a patterned cathode demonstrate a ~20% higher accessible capacity than those without at 1.4C. Additionally, 1C capacity retention of cells with patterned cathode (91% through 3000 cycles) is significantly improved over cells with only the anode patterned (64%) and non-patterned electrodes (50%). Characterization of post-mortem cells before and after refreshing their electrolyte suggests that 1C capacity retention is improved by mitigation of electrode "dry-out". We hypothesize that the microstructure acts as a reservoir of additional electrolyte, or a path for gas to escape, so that active material remains wetted throughout long-term cycling, and/or the microstructure may reduce localized, gas-forming overpotentials in the high-loading electrode.

25 ENERGY STORAGE↗
DOE OSTI2017

Developing Cost-Effective Dense Continuous SDC Barrier Layers for SOFCs

Significantly improved performance during electrochemical testing of a cell with a dense continuous pulsed laser deposited (PLD) samarium doped ceria (SDC) layer spurred investigations into the fabrication of dense continuous SDC barrier layers by means of cost-effective deposition using screen printing which is amenable to industrial production of SOFCs. Many approaches to improve the SDC density have been explored including the use of powder with reduced particle sizes, inks with increased solids loading, and doping with sintering aids (1). In terms of sintering aids, dopants like Mo or binary systems of Mo+Cu or Fe+Co greatly enhance SDC sinterability. In fact, adding dopants to a screen printed, prefired, porous SDC layer made it possible to achieve a dense continuous barrier layer atop the YSZ electrolyte without sintering above 1200°C. Although the objective of fabricating a dense continuous layer was achieved, additional studies have been initiated to improve the cell performance. Underlying issues with constrained sintering and dopant-enhanced ceria-zirconia solid solubility are also addressed in this paper.

Nguyen, Hoang Viet P.↗
DOE OSTI2022

Spectroscopic signatures and oxidation characteristics of nanosecond laser-induced cerium plasmas

Improving technologies related to the wide area environmental sampling of nuclear materials supports the nuclear nonproliferation mission of preventing the proliferation of nuclear weapons by monitoring nuclear weapons tests and detecting undeclared nuclear fuel cycle activities. Standoff, laser-based detection techniques such as laser-induced breakdown spectroscopy have the potential to offer robust, field-deployable methods that provide rapid element-specific and phase identifiable measurements over a wide range of materials. This work aims to elucidate the effects of atmospheric conditions and oxidation reactions on the highly complex and transient spectroscopic signatures of laser-induced plutonium surrogate plasmas. Time-resolved spectra of nanosecond laser ablation cerium plasmas were measured using laser-induced breakdown spectroscopy in a range of atmospheres containing low to high concentrations of oxygen. Here, the growth of strong CeO molecular emission bands was observed in the visible spectrum, where it was shown that the persistence of CeO is reduced from around 60 μs to 50 μs in oxygen rich atmospheric environments. To further investigate the growth and depletion of CeO in the laser-produced plasma, ratios of CeO-to-Ce emission were generated using integrated intensities corresponding to the Q-branch of the CeO D 1 -X 1 transitions and numerous strong atomic Ce peaks. It was determined that the fastest rate of formation of CeO in argon occurred for moderate oxygen mass fractions between 0.10 and 0.15 while the ratios were reduced at higher oxygen mass fractions (i.e., Y O 2 = 0.20) due to competing oxidation reactions and lower plasma temperatures.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

Developing Methodology to Determine Pu Isotopic Composition by Laser Ablation MC-ICP-MS

This project will develop methodology to analyze the Pu isotope ratio in mixed U-Pu particles by laser ablation MC-ICP-MS. This will involve: 1) testing and validation of the Pu analytical method using mixed U-Pu solutions and Pu doped glasses, 2) isotopic analysis of mixed U-Pu particles by laser ablation MC-ICP-MS, and 3) continued development of the R-based data reduction program. Details regarding the analytical method development and results of QC testing will be output as a deliverable to the IAEA, along with an updated version of the LARA data reduction software.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Development of TDLAS for Water Vapor Concentration Measurement during VHTR Steam Ingress

Very-high-temperature reactors (VHTR) utilize a graphite-moderated, helium-cooled design that provides higher efficiencies and a low-carbon source of process heat (>700 deg. C) for many industrial applications. Safety concerns have led to extensive accident condition investigations. Steam generator heat-exchanger tube rupture accidents (SGTR) can lead to increased reactor core steam density, which causes neutron slowing-down and chemical corrosion of the graphite fuel elements and structural columns. It is important to be able to computationally model the propagation of steam throughout the lower plenum and nuclear reactor core, but experimental data is needed to validate such models. The primary objective of this project is to instrument a scaled down experiment of a VHTR designed by Ohio State University (OSU), with tunable diode laser absorption spectroscopy (TDLAS) diagnostics to measure steam concentration changes and map how water vapor propagates through the test facility's lower plenum and core. The basic principle of absorption spectroscopy is based on a molecular species ability to absorb photons of specific energies. A collimated laser beam of known energy is passed through a test section containing a sample gas. When a transition of the absorbing gas species resonates with the laser frequency, a certain amount of energy will be absorbed based on the rovibrational characteristics of the molecule. The intensity of the transmitted laser light can be measured by a detector after exiting the test section. The Beer-Lambert Law of absorbance is used to recover this information relating beam attenuation to the system dimensions, gas composition, pressure, and temperature. The line-strength is a function of temperature alone and relates the fraction of molecules in a given rovibrational state through the partition function. The partition function describes the statistical properties of a system in thermodynamic equilibrium where the states obey a Boltzmann distribution. Thus, the number density of molecules in a particular state can be determined from the total internal partition function at a particular temperature. The lineshape function of a given absorption transition is derived from the physical interaction between the absorbing species and is dependent on temperature and pressure. Random thermal motion of absorbing molecules result in broadening of the linewidth, called Doppler broadening, which follows a Gaussian distribution. Molecular collisions result in broadening and shifting of the linewidth, called pressure broadening, which follows a Lorentzian distribution. The overall lineshape results in a Voigt profile, which is a convolution of the Gaussian and Lorentzian distributions. The Voigt profile does not have a simple analytical form and is most often calculated numerically or approximated by complex functions. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS2018

New Technologies Advancing Thermophysics

Researchers at NASA Ames in California have built a new facility that uses multiple 50-kW continuous wave lasers to add the capability for simulating radiative heating on thermal protection materials. The new facility, the Laser Enhanced Arc-jet Facility (LEAF-Lite), was added to NASA Ames’s Interaction Heating Facility arc-jet and now allows for test articles to be heated by both convective and radiative heat flux, making the facility more like flight. Using this new system, researchers can now simulate radiant heating with the laser and convective heating with the arc-jet simultaneously on a single test article. During its initial test in October 2017, the lasers radiatively heated a 6” x 6” Avcoat wedge sample to 405 W/sq.cm while the arc-jet simultaneously provided 160 W/sq.cm of convective heat, resulting in a total heat flux of 565 W/sq.cm. Radiative heating is more prevalent in missions with higher atmospheric entry speeds like the Orion space capsule or interplanetary scientific probes. Later this year, scientists will expand the spot size to cover 17” x 17” to test an Orion TPS panel.

Brandis, Aaron↗
NASA NTRS2003

Trailing Vortex Measurements in the Wake of a Hovering Rotor Blade with Various Tip Shapes

This work examined the wake aerodynamics of a single helicopter rotor blade with several tip shapes operating on a hover test stand. Velocity field measurements were conducted using three-component laser Doppler velocimetry (LDV). The objective of these measurements was to document the vortex velocity profiles and then extract the core properties, such as the core radius, peak swirl velocity, and axial velocity. The measured test cases covered a wide range of wake-ages and several tip shapes, including rectangular, tapered, swept, and a subwing tip. One of the primary differences shown by the change in tip shape was the wake geometry. The effect of blade taper reduced the initial peak swirl velocity by a significant fraction. It appears that this is accomplished by decreasing the vortex strength for a given blade loading. The subwing measurements showed that the interaction and merging of the subwing and primary vortices created a less coherent vortical structure. A source of vortex core instability is shown to be the ratio of the peak swirl velocity to the axial velocity deficit. The results show that if there is a turbulence producing region of the vortex structure, it will be outside of the core boundary. The LDV measurements were supported by laser light-sheet flow visualization. The results provide several benchmark test cases for future validation of theoretical vortex models, numerical free-wake models, and computational fluid dynamics results.

Martin, Preston B.↗
NASA NTRS1990

Transceiver for Space Station Freedom

This paper describes the design of the Laser Communication Transceiver (LCT) system which was planned to be flight tested as an attached payload on Space Station Freedom. The objective in building and flight-testing the LCT is to perform a broad class of tests addressing the critical aspects of space-based optical communications systems, providing a base of experience for applying laser communications technology toward future communications needs. The LCT's functional and performance requirements and capabilities with respect to acquisition, spatial tracking and pointing, communications, and attitude determination are discussed.

Fitzmaurice, M.↗
NASA NTRS2018

Importance of Measuring SiC Fiber Diameter Prior to Conducting Fiber Stress Rupture / Creep Tests?

A very significant amount of SiC fiber creep / stress rupture data has been generated and reported in the past by various researchers. Due to the difficulty of measuring fiber diameter and the amount of time required to make accurate measurements, researchers have quite often used an accepted average diameter value (which is fiber type-dependent) when determining the load that will be applied to a fiber to generate a specific stress during testing. Of course, this approach has less of an effect on data scatter when the individual fibers in a tow have very similar diameters (minimal fiber-to-fiber variation in diameter). NASA GRC has begun using a laser fiber diameter measurement system, and we are considering eventually characterizing each SiC fiber prior to testing in creep/stressed oxidation. The laser system will be described in this presentation, as well as examples of fiber diameter data obtained in the past at AFRL. We are currently discussing the merits of using an average diameter in testing/data analysis vs. using a measured or "known" diameter. Information about our current intermediate temperature SiC fiber stress rupture testing will also be provided.

ceramic matrix composites↗
DOE OSTI2013

Large dynamic range diagnostics for high current electron LINACs

The Jefferson Lab FEL driver accelerator - Energy Recovery Linac has provided a beam with average current of up to 9 mA and beam energy of 135 MeV. The high power beam operations have allowed developing and testing methods and approaches required to set up and tune such a facility simultaneously for the high beam power and high beam quality required for high performance FEL operations. In this contribution we briefly review this experience and outline problems that are specific to high current - high power non-equilibrium linac beams. While the original strategy for beam diagnostics and tuning have proven to be quite successful, some shortcomings and unresolved issues were also observed. The most important issues are the non-equilibrium (non-Gaussian) nature of the linac beam and the presence of small intensity - large amplitude fraction of the beam a.k.a. beam halo. Thus we also present a list of the possible beam halo sources and discuss possible mitigations means. We argue that for proper understanding and management of the beam halo large dynamic range (>10{sup 6}) transverse and longitudinal beam diagnostics can be used. We also present results of transverse beam profile measurements with the dynamic range approaching 10{sup 5} and demonstrate the effect the increased dynamic range has on the beam characterization, i.e., emittance and Twiss parameters measurements. We also discuss near future work planned in this field and where the JLab FEL facility will be used for beam tests of the developed of new diagnostics.

43 PARTICLE ACCELERATORS↗
NASA NTRS1995

Energy measurement of electron beams by Compton scattering

A method has been proposed to utilize the well-known Compton scattering process as a tool to measure the centroid energy of a high energy electron beam at the 0.01% level. It is suggested to use the Compton scattering of an infrared laser off the electron beam, and then to measure the energy of the scattered gamma-rays very precisely using solid-state detectors. The technique proposed is applicable for electron beams with energies from 200 MeV to 16 GeV using presently available lasers. This technique was judged to be the most viable of all those proposed for beam energy measurements at the nearby Continuous Electron Beam Accelerator Facility (CEBAF). Plans for a prototype test of the technique are underway, where the main issues are the possible photon backgrounds associated with an electron accelerator and the electron and laser beam stabilities and diagnostics. The bulk of my ASEE summer research has been spent utilizing the expertise of the staff at the Aerospace Electronics Systems Division at LaRC to assist in the design of the test. Investigations were made regarding window and mirror transmission and radiation damage issues, remote movement of elements in ultra-high vacuum conditions, etc. The prototype test of the proposed laser backscattering method is planned for this December.

Keppel, Cynthia↗
DOE OSTI2023

Broadband, 920-nm mirror thin film damage competition

This year’s competition proposed to survey the state-of-the-art broadband, near-IR multilayer dielectric (MLD) mirrors designed for ultra-short, pulsed laser applications. The requirements for the coatings were a minimum reflection of 99.5% at 45-degree incidence angle for S-polarization from 830 nm to 1010 nm and group delay dispersion (GDD) < ± 50 fs 2 . The participants in this effort selected the coating materials, coating design, and deposition method. Samples were damage tested at a single testing facility to enable direct comparison among the participants using a 25 ± 5 fs OPCPA laser system operating at 5 Hz. A double blind test assured sample and submitter anonymity. The damage performance results, sample rankings, details of the deposition processes, coating materials and substrate cleaning methods are shared here. We found that multilayer coatings using tantala and/or hafnia as high index materials were top performers within several coating deposition groups. Specifically, dense coatings by ion-beam sputtering (IBS), magnetron sputtering (MS), and electron-beam ion assisted deposition (e-beam IAD) exhibited highest damage initiation onset (LIDT) while e-beam coatings were low performers. In addition, damage growth onset (LDGT) was also examined and the results are reported here for all samples as this performance metric plays an important role in establishing the safe operational conditions for larger aperture, ultrashort pulsed lasers. As a result, not all coating samples in the survey met the GDD requirements stated above and associated measurements are discussed in the context of the present and past competitions focused on similar broadband, near-IR MLD coatings.

42 ENGINEERING↗
DOE OSTI2018

Tribological Behavior of Electrochemically Etched AISI 316 Stainless Steel with a Textured Surface

In this work, AISI 316 stainless steel (316 SS) was electrochemically etched in four NaCl solutions (10, 15, 20, and 25 wt.%) to form textured surfaces. Surface morphologies, three-dimensional surface topographies, and surface profiles of the textured 316 SS samples were obtained by scanning electron microscopy (SEM) and laser scanning confocal microscope (LSCM). Sliding friction tests of the textured 316 SS samples were conducted in air and under grease lubrication. The results suggested that the variable degrees of microtextured surfaces after electrochemical etching in 10, 15, and 20 wt.% NaCl solutions. The 316 SS samples etched in 15 and 20 wt.% NaCl solutions showed more promising tribological performance than other samples, as reflected by their friction coefficients, mass loss per unit distance traveled (mg/m), and wear morphologies.

36 MATERIALS SCIENCE↗
DOE OSTI2015

High-frequency sarcomeric auto-oscillations induced by heating in living neonatal cardiomyocytes of the rat

Highlights: • We tested the effects of infra-red laser irradiation on cardiac sarcomere dynamics. • A rise in temperature (>∼38 °C) induced high-frequency sarcomeric auto-oscillations. • These oscillations occurred with and without blockade of intracellular Ca{sup 2+} stores. • Cardiac sarcomeres can play a role as a temperature-dependent rhythm generator. - Abstract: In the present study, we investigated the effects of infra-red laser irradiation on sarcomere dynamics in living neonatal cardiomyocytes of the rat. A rapid increase in temperature to >∼38 °C induced [Ca{sup 2+}]{sub i}-independent high-frequency (∼5–10 Hz) sarcomeric auto-oscillations (Hyperthermal Sarcomeric Oscillations; HSOs). In myocytes with the intact sarcoplasmic reticular functions, HSOs coexisted with [Ca{sup 2+}]{sub i}-dependent spontaneous beating in the same sarcomeres, with markedly varying frequencies (∼10 and ∼1 Hz for the former and latter, respectively). HSOs likewise occurred following blockade of the sarcoplasmic reticular functions, with the amplitude becoming larger and the frequency lower in a time-dependent manner. The present findings suggest that in the mammalian heart, sarcomeres spontaneously oscillate at higher frequencies than the sinus rhythm at temperatures slightly above the physiologically relevant levels.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Process development of 99.95% pure copper processed via selective electron beam melting and its mechanical and physical properties

Highlights: • Additively manufactured dense copper samples (>99.5%) • Measured electrical conductivity >58 MS/m (>100% IACS) • Equiaxed grain structure • 177 N/mm{sup 2} tensile strength, 87 N/mm{sup 2} yield strength, 59% elongation at fracture - Abstract: Additive manufacturing by selective electron beam melting (SEBM) was used to fabricate pure copper specimens. A process window at process temperature of 530 °C, gives the required beam powers and deflection speeds for manufacturing dense specimens (>99.5%). The microstructure of SEBM specimens was analyzed by using optical and scanning electron microscopy (SEM). Electrical conductivity, thermal conductivity, hardness, and mechanical performance were investigated by using eddy current, laser flash analysis, Vickers hardness and tensile tests, respectively. It was found that the variation of beam power and scan speed results in different microstructures from columnar to nearly equiaxed grain. The electrical conductivity of SEBM-processed specimens was above 58 MS/m (>100 IACS) while their hardness was around 55 HV0.05 and 46 HV5 without any dependency on processing parameters within the process window. The tensile tests revealed how vertical cracks affect the mechanical strength under tensile loading condition. The results of this study not only show a reliable process window but also introduce the links between processing parameters, defect formations, conductivity and mechanical strength of pure copper specimens manufactured by SEBM.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Electrical conductivities of (Mg,Fe)O at extreme pressures and implications for planetary magma oceans

During planet formation, planets undergo many impacts that can generate magma oceans. When these crystallize, part of the magma densifies via iron enrichment and migrates to the core–mantle boundary, forming an iron-rich basal magma ocean (BMO). The BMO could generate a dynamo in early Earth and super-Earths if the electrical conductivity of the BMO, which is thought to be sensitive to its Fe content, is sufficiently high. To test this hypothesis, here we conduct laser-driven shock experiments on ferropericlase (Mg x ,Fe 1−x )O (0.95 ≤ x ≤ 1) as an Fe-rich BMO analogue, perform density functional theory molecular dynamics simulations on MgO and calculate the long-term evolution of super-Earths. We find that the d.c. conductivities of MgO and (Mg,Fe)O are indistinguishable between 467 GPa and 1,400 GPa, despite previous predictions. Here, we predict that super-Earths larger than 3–6 Earth masses can produce BMO-driven dynamos that are almost one order of magnitude stronger than core-driven dynamos for several billion years.

Exoplanets↗
DOE OSTI2014

Structural phase transition and erasable optically memorized effect in layered γ-In{sub 2}Se{sub 3} crystals

We have grown In{sub 2}Se{sub 3} layered-type crystals using chemical vapor transport method with ICl{sub 3} as the transport agent. The as-grown crystals show two different color groups of black shiny for α-phase In{sub 2}Se{sub 3} and red to yellow for γ-phase In{sub 2}Se{sub 3}. High-resolution transmission electron micro scopy verifies crystalline state and structural polytype of the as-grown In{sub 2}Se{sub 3}. The results indicate that the α-In{sub 2}Se{sub 3} crystals present more crystalline states than those of the other amorphous γ-In{sub 2}Se{sub 3}. The amorphous effect on the advancing of optoelectronic property of γ-In{sub 2}Se{sub 3} shows erasable optical-memorized effect in the disordered and polycrystalline γ-In{sub 2}Se{sub 3} layers. Laser-induced photodarkening and annealed-recovery test verified that a reversible structural-phase transition of γ↔α can occur inside the γ-In{sub 2}Se{sub 3}. Thermoreflectance and Raman scattering measurements are carried out to identify the inter-phase transformation of the γ-In{sub 2}Se{sub 3} polycrystals using different heat treatments. Direct band gaps and Raman vibration modes for the γ- and α-In{sub 2}Se{sub 3} crystalline phases are, respectively, characterized and identified. The character of γ↔α inter-phase transition promotes feasible optical and optoelectronic applications of the γ-In{sub 2}Se{sub 3} material in optical memory, optics, and solar-energy devices.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗